Gas Water Heater Exhaust Ducting Fire Prevention

[DEK]

My 40 gallon gas water heater is located in my basement. It has Selkirk Type B, 4 inch exhaust ducting going up inside an insulated wall between my family room and garage and out through the garage ceiling. My understanding is that these ducts require a minimum of one inch away from any combustibles. Is this correct?

If yes, is fiberglass insulation considered combustible? If yes, how to I insulate the wall in the photo and still keep the insulation away from the duct? Or is it okay to allow the insulation to touch the duct?

Thank you,
Don

 

[Breplum]

Yes, 1" min. clearance to combustibles and with proper clamps to maintain the 1". Fiberglass without backing paper is not flammable and fine for contact.

 

[Sponsor]

 

[Fitter30]

Look at fig 5 they call for 1"

https://www.google.com/url?q=https://www.selkirkcorp.com/literature/Model_RV_Installation_Instructions.pdf&sa=U&ved=2ahUKEwiB1fbNv9n-AhUDk4kEHTvdAkMQFnoECAkQAg&usg=AOvVaw030bQAv9QFRABN1fEZYh_Z

 

[John Gayewski]

If it were me, most of that stud bay would stay uninsulated. If anything maybe a portion of it would get insulated but you'd need another piece of wood to keep it from moving.